Serotonin (5-HT7) receptor-stimulated activation of cAMP-PKA pathway in bovine corneal epithelial and endothelial cells.

BACKGROUND: 5-Hydroxytryptamine (5-HT; serotonin) is a major neurotransmitter, and its receptors are found throughout the whole body. The 5-HT7 receptor subtype was detected in human corneal epithelial and endothelial cells and found to be functionally active in a corneal epithelial cell line. The aim of the present study was to demonstrate that native bovine corneal epithelial and endothelial cells express a functional 5-HT7 receptor positively coupled to adenylyl cyclase and protein kinase A (PKA) formation. METHODS: 5-HT7 receptors were studied using polyclonal antibodies. cAMP concentration after 5-HT7 receptor stimulation with 5-carboxamidotryptamine (5-CT, a 5-HT7 agonist) was tested by enzyme immunoassay, PKA activity was estimated by kinase consumption of ATP. RESULTS: Immunocytochemistry and immunofluorescence revealed the presence of 5-HT7 receptors in corneal epithelial and endothelial cells. Stimulation of corneal 5-HT7 receptors with 5-CT revealed a dose-dependent increase in intracellular cAMP concentration in corneal epithelium (0.01-0.34 pmol/ml) and endothelium (0.01-0.19 pmol/ml) between 10(-10) and 10(-7) mg/ml 5-CT (p = 0.001) with maximal stimulation from 10(-7) to 10(-3) mg/ml 5-CT (0.30 ± 0.03 and 0.18 ± 0.01 pmol/ml, respectively). Incubation with 10(-6) mg/ml SB269970 (a selective 5-HT7 antagonist) blocked 5-CT-induced cAMP increase in corneal epithelial (0.03 pmol/ml) and endothelial cells (0.02 pmol/ml; p = 0.001). Stimulation of corneal 5-HT7 receptors with 5-CT revealed a dose-dependent increase in PKA activity between 10(-10) and 10(-8) mg/ml 5-CT in corneal epithelium and endothelium (<1 to >99%; p = 0.013 and p = 0.017, respectively) with maximal stimulation from 10(-8) to 10(-4) mg/ml (>99%) 5-CT. CONCLUSIONS: Our data demonstrate that native corneal epithelial and endothelial cells express a functional 5-HT7 receptor positively coupled to adenylyl cyclase and PKA formation. However, at the present time, the physiological role of 5-HT receptors and the cAMP-PKA pathway in the cornea remains a matter of speculation.

Reporting of Safety Events during Anti-VEGF Treatment: Pharmacovigilance in a Noninterventional Trial.

AIM: The prospective, noninterventional OCEAN study assessed the safety of intravitreal ranibizumab injections for treatment of neovascular age-related macular degeneration, diabetic macular edema, and retinal vein occlusion under real-world conditions in Germany. METHODS: Adults receiving ≥1 ranibizumab (0.5 mg) injections were recruited by 369 ophthalmologists and followed for 24 months. Information on adverse events (AEs) was reported by the treating physician or detected by the data management team. Collected information included observed AE, AE start and end date, intensity, causal relationship, outcome, severity, suspected drug, and actions taken. RESULTS: 2,687 AEs were reported for 1,176 of the 5,781 patients who had received a total of 32,621 injections: 27.4% nonserious AEs, 30.3% serious AEs, 27.3% nonserious adverse drug reactions (ADRs), and 15.0% serious ADRs. Most patients reported no AEs (79.7%) or only 1 AE (10.3%). AEs were most commonly reported in the Medical Dictionary for Regulatory Activities (MedDRA) System Organ Class (SOC) Eye disorders (9.4% of patients) and General disorders and administration site conditions (5.8%). The most frequent AEs by MedDRA preferred term (PT) were visual acuity reduced (3.5% of patients), intraocular pressure increased (2.5%), and drug ineffective (2.1%). AEs occurred most frequently after 3 or 4 injections (1,129 of 2,687 AEs). The proportion of AEs in the SOC Eye disorders decreased slightly with increasing number of injections, from 39.8% of events after 1 or 2 injections to 29.1% after 5 or more injections. Rates of the most frequently reported PTs did not show any consistent increase with increasing number of injections. A decrease in overall AE rates was observed over the study course. CONCLUSIONS: The results did not raise any new safety concerns for ranibizumab. The findings allow conclusions to be drawn on how pharmacovigilance data can be collected even more effectively in real-world studies to facilitate discussion on benefit-risk ratio.

Adrenergic regulation of cAMP/protein kinase A pathway in corneal epithelium and endothelium.

PURPOSE: The G-protein-coupled receptor/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway is one of the most common and versatile signal pathways in eukaryotic cells. The aim of this study was to characterize subtypes of adrenergic G-protein-coupled receptors and their influence on cAMP concentration and PKA activity in bovine corneal epithelial and endothelial cells. PROCEDURES: Adrenergic receptors and PKA were studied using polyclonal antibodies. cAMP concentration was determined with an enzyme immunoassay, and PKA activity was estimated by the kinases consumption of adenosine triphosphate. RESULTS: In bovine corneal epithelial and endothelial cells, immunocytochemistry and Western blot were positive for alpha(1)-, alpha(2A)-, beta(1)- and beta(2)-adrenergic receptors. Stimulation of corneal epithelial and endothelial beta-adrenoceptors with isoprenaline led to a dose-dependent increase in cAMP concentration and activation of PKA. Stimulation of corneal alpha(2A)-adrenoceptors with brimonidine resulted in a dose-dependent decrease in cAMP concentration and the inhibition of PKA activity. CONCLUSIONS: In corneal epithelial and endothelial cells, beta-adrenergic stimulation leads to activation of PKA via stimulation of adenylyl cyclase, and alpha(2A)-adrenoceptor stimulation inhibits PKA activity via inhibition of adenylyl cyclase. Stimulation and inhibition of the corneal cAMP-PKA pathway may play a role in important corneal functions such as wound healing or homeostasis. Long-term therapy with alpha(2A)-agonists or beta-antagonists may influence these functions in a currently unknown way.

Amphotericin B in the therapy of Candida glabrata endophthalmitis after penetrating keratoplasty.

PURPOSE: Candida glabrata is a rare cause of endophthalmitis after penetrating keratoplasty. Adequate therapy is still under discussion. With respect to severe complications and side effects of antifungal therapy, a substantial knowledge of sensitivity and resistance of the organism is necessary. METHODS: We report on a 26-year-old man with a hyperacute onset of the infection only 10 hours after surgery. A combined therapy for fluconazole and steroids administered over 3 months had shown no effect on intraocular infection. RESULTS: After topical and intracameral application of amphotericin B in combination with topical prednisolone 3 months after the onset of the endophthalmitis, the infection disappeared within 14 days, and the graft remained clear for 2 months. No toxic effects were noticed. CONCLUSION: In the case presented here, topical and intracameral application of amphotericin B was sufficient and safe in the therapy for C. glabrata endophthalmitis after penetrating keratoplasty. Although typically the intraocular infection is first noticed within the first 2 weeks, a hyperacute onset has to be considered.

Effect of timolol on central corneal thickness.

PURPOSE: Timolol is an effective and safe medication that is widely used in glaucoma treatment. Although it is known that it is quickly taken up by the cornea following topical administration and that the cornea exhibits -adrenergic receptors, there are few studies available on the clinical impact of timolol on central corneal thickness (CCT). METHODS: Twenty healthy subjects were tested in a double-blind, prospective, and randomized study. Intraocular pressure (IOP) and CCT were measured before and during administration of timolol 0.5% eyedrops over 28 days. RESULTS: Administration of timolol 0.5% resulted in a reduction of IOP from an initial value of 16 ± 2 mm Hg to 13 ± 0 mm Hg (p<0.001, R2 = 0.7033) as well as an increase in CCT from 555 ± 11 µm from the time of the baseline examination to 567 ± 9 µm (p = 0.005, R2 = 0.8754), an increase of epithelial thickness from 53 ± 2 µm to 59 ± 3 µm (p<0.001, R2 = 0.5063), and an increase of stromal thickness from 494 ± 4 µm to 498 ± 9 µm (p = 0.045, R2 = 0.4352) after 9 days each. From day 10 on, a decrease in CCT (R2 = 0.6164), epithelial thickness (R2 = 0.2216), and stromal thickness (R2 = 0.2092) was observed. At the end, the values had returned toward the initial values measured (CCT 553 ± 8 µm, p = 0.391; epithelial thickness, 50 ± 2 µm, p = 0.214; and stromal thickness, 493 ± 8 µm, p = 0.483). In contrast, endothelial thickness did not vary following administration of timolol 0.5% (p = 0.727, R2 = 0.009). CONCLUSIONS: Topical administration of timolol 0.5% results in a reversible increase in CCT. These modest changes are unlikely to influence tonometry or clinical decision-making.

Effect of brimonidine on corneal thickness.

PURPOSE: Brimonidine, an alpha-2 adrenoceptor agonist, is an effective and safe medication that is widely used in glaucoma treatment. Although it is known that it is quickly taken up by the cornea following topical administration and that the cornea has alpha-2 adrenoceptors, there are only few studies available on the impact brimonidine has on the cornea. METHODS: Twenty healthy test persons (12 female and 8 male subjects)-mean age about 33 years (22 to 38 years)-were tested in a double-blind, prospective, randomized study. Intraocular pressure as well as epithelial, stromal, and endothelial thickness was measured before, at 25 days while, and at 5 days after administration of brimonidine 0.1% eye drops twice daily. To check the impact of this medication, placebo (proper solution of preservative) eye drops were administered to the other eye twice daily. RESULTS: Administration of brimonidine 0.1% resulted in a reduction of intraocular pressure from an initial value of 14 to 9 mmHg after 5 days (P=0.001) as well as an increase in total corneal thickness from 556 µm from the time of the baseline examination to 578 µm (P=0.001), an increase of epithelial thickness from 58 to 66 µm (P<0.001), and stromal thickness from 488 to 502 µm (P=0.008) after 2 days each. Another 2 days later, total corneal thickness was 559 µm (P=0.276), epithelial thickness 56 µm (P=0.561), and stromal thickness 493 µm (P=0.315), which means that the values had returned more or less toward the initial values measured. In contrast, endothelial thickness did not vary following administration of brimonidine 0.1% (P=0.965). With treatment with brimonidine 0.1%, mean intraocular pressure in thin corneas (<556 µm) was lower than in the thick corneas (>556 µm, P=0.018). CONCLUSIONS: Topical administration of brimonidine 0.1% results in a reversible increase in corneal thickness. The question whether this increase is of clinical significance and whether it is the result of epithelial and/or endothelial receptor stimulation cannot be finally answered at the present time.

Muscarinic cholinoceptor-stimulated phosphatidyl inositol pathway in corneal epithelial and endothelial cells.

BACKGROUND: Muscarinic cholinoceptors are distributed widely in both the central and peripheral nervous system. The presence of muscarinic cholinoceptors in corneal tissue is well established. Previous reports have shown that corneal muscarinic cholinoceptors are of the m2 or m4 subtype. However, recent studies have indicated the presence of the m5 muscarinic cholinoceptor subtype in human corneal epithelium and endothelium. The aim of the study was to confirm the presence of the m5 cholinoceptor subtype in bovine corneal epithelium and endothelium and the activation of phosphatidyl inositol pathway by its stimulation. METHODS: Muscarinic m5 cholinoceptor sites, phosphatidyl inositol 4,5-biphosphate, inositol 1,4,5-triphosphate and protein kinase C, were studied using immunocytochemistry and immunofluorescence. Activation of protein kinase C after stimulation of the m5 muscarinic cholinoceptor subtype was measured using the HTS protein kinase C assay kit. RESULTS: Immunocytochemistry/immunofluorescence revealed the presence of the m5 muscarinic cholinoceptor subtype, phosphatidyl inositol 4,5-biphosphate and protein kinase C in bovine corneal epithelial and endothelial cells. In bovine corneal epithelium and endothelium, protein kinase C activity was stimulated by acetylcholine in a dose-dependent manner (P<0.0001). CONCLUSIONS: Our findings indicate that acetylcholine-induced stimulation of muscarinic m5 cholinoceptors activates the phosphatidyl inositol pathway in corneal epithelial and endothelial cells, resulting in increased protein kinase C activity. Further work will be needed to clear the physiologic role of this signaling pathway in corneal epithelium and endothelium.

Transscleral diode laser cyclophotocoagulation as primary and secondary surgical treatment in primary open-angle and pseudoexfoliatve glaucoma. Long-term clinical outcomes.

BACKGROUND: Transscleral diode laser cyclophotocoagulation (TDLC) has been used successfully in the treatment of refractive glaucoma. However, little is known about TDLC as a primary or secondary surgical procedure in primary open-angle and pseudoexfoliative glaucoma. METHODS: In a retrospective chart review we analyzed 90 eyes (48 OD/42 OS) in 90 patients (mean age 75 years, range 60-92 years; 51 men/39 woman) with primary open-angle glaucoma (n=66) and pseudoexfoliative glaucoma (n=24) who consecutively underwent TDLC with a minimum follow-up of 24 months. In 24 eyes (26.7%) TDLC was the primary surgical treatment. Mean energy was 80 J (60-92 J). Success was defined as a final intraocular pressure (IOP) between 4 and 18 mmHg, a minimum IOP reduction of 20% and the absence of major complications. RESULTS: The overall success rate was 36.7% after 24 months. A mean of 1.3 procedures was performed per patient. No correlation between age and success rate (p=0.887) or gender and success rate (p=0.895) was seen. There was no significant reduction in antiglaucomatous medication (p=0.208), no significant loss of visual acuity (p=0.324) nor a significant relationship between loss of visual acuity and failure of treatment (p=0.201). In patients with primary open-angle glaucoma the success rate was 40.9% after 24 months; in patients with pseudoexfoliative glaucoma it was 25.0% after 24 months. There was no significant difference between primary open-angle glaucoma and pseudoexfoliative glaucoma (p=0.684). Previous ocular surgery decreased the success probability from 45.8 to 33.3% (p=0.001). Prolonged hypotonia occurred in 1 patient. No phthisis bulbi developed. CONCLUSIONS: Transscleral diode laser cyclophotocoagulation is an effective and safe method not only in the treatment of refractive glaucoma, but also as a primary surgical procedure in primary open-angle and pseudoexfoliative glaucoma. TDLC may be used more widely in glaucoma therapy, although further long-term studies have to confirm these findings.

Muscarinic acetylcholine receptor subtypes in human corneal epithelium and endothelium.

BACKGROUND: Muscarinic acetylcholine receptors are located throughout the body. The demonstration of muscarinic receptors in corneal tissue has been inconsistent. Using freshly fixed human corneal tissue, we show a complete profile of muscarinic receptor subtypes in human corneal epithelium and endothelium. METHODS: Muscarinic receptor sites were studied using immunocytochemistry, immunofluorescence and immunoblotting. RESULTS: Antibodies to M2, M4 and M5 muscarinic receptor subtypes bound in human corneal epithelium and endothelium. No binding was found for antibodies to M1 and M3 muscarinic receptor subtypes. CONCLUSIONS: Our studies indicate the presence of M2, M4 and M5 muscarinic acetylcholine receptor subtypes in human corneal epithelium and endothelium. These receptors may play a role in the regulation of corneal homeostasis, other functions, like wound healing, or the pathogenesis of corneal diseases.

Monoamine receptors in human corneal epithelium and endothelium.

PURPOSE: Monoamine receptors are found throughout the body. Reports about the presence of monoamine receptors in the human cornea are inconsistent. METHODS: Immunohistochemistry, immunofluorescence and immunoblotting were used to localize monoamine receptor sites on human corneal epithelium and endothelium. RESULTS: Antibodies to alpha-1, beta-1 and beta-2 adrenergic receptors and to D1-like and 5HT-7 receptors were bound in corneal epithelium. Antibodies to alpha-1, alpha-2A, beta-1 and beta-2 adrenergic receptors and to 5HT-7 receptors were bound in corneal endothelium. CONCLUSIONS: Our data demonstrate the presence of several monoamine receptors in the human cornea. These receptors may play a role in the regulation of fluid transport or corneal homeostasis.